Apparatus for counterbalancing disturbances in telephones



(No Mo deI.) I A. BERNSTBIN.

APPARATUS FOR GOUNTERBALANUING D ISTURBANGES IN TELEPHONES. No. 286,577. Patented 001;. 16, 1883.

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UNiTED STATES PATENT OFF CE.

ALEX; BERNSTEIN, OF BOSTON, MASSACHUSETTS;

APPARATUS FOR COUNTERBALANCING DlSTURBA-NCES IN TELEPHONES.

SPEGIFIGATTON: forming part of Letters Patent No. 286,577, dated October 16, 1883.

' Application liled May 14. 1883. (N model.)

To all whom it .may concern."

Be it known that I, ALnx. BERNSTEIN, of Boston, in the county of Suffolkand State of Massachusetts,'have invented a certain Im- I uponby such-currents. Thetelephone is, how

and in some cases impossible.

ever, in virtue of its excessive sensibility, liable to be influenced greatly by foreign electrical currents induced in its conducting-wire by the currents traversing other conducting-wires adjacent thereto. Moreover, thesev induced currents frequently act so strongly upon the telephone-circuit, and, consequently, in the telephone itself, as to drown the articulations,

and to render oral communication difficult, Particularly is this the case when the telephone-wire extends for a long distance parallel with or adjacentto' other wires, conveying relatively strong currents-such as those used in telegraphy or electriclighting while the annoyance is also considerable even when the disturbingwire conveys a telephonic current also.

The object of my. invention is to counterbalance, compensate, or neutralize the effects of this induction in an effectual, simple, and

economical manner, and thus to render the operation of long lines practicable even when they are extended upon supports already utilized for other conducting-wires. By the achievement of this object telephone-wires may be extended upon a system of poles upon which, for example, telegraphwires are supported, while heretofore special supports have been essential, and the telephonic communication may then be readily established between any two or more points which would, on the score of economy, remain unconnected were a special line of supports necessary. Railways may also avail themselves of this invention to utilize the telephone-wire as a medium of com This, how ever, is only sufficient when the wires are near to one another and both wires equidistant from the disturbing-wire5 and is, more over, objectionable from the fact that twice the amount of line-wire and twice the labor in construction become necessary. In order to attain the desired object, I make use of a compensating-circuit, and by a peculiar construction of the receiving-telephones and ar rangement of the circuit-in connection with the said telephones the induction is neutralized in the telephone, while the articulations are emitted clearly and distinctly. This compensating-circuit, as I shallhereinafter show and describe, may consist of an extra linewire, which either extends along the whole or a part of the telephone circuit-line, or which is entirely placed in the receiving-station, and in this later case takes the forin of an induc tion-coil. l

' I shall describe, first, theconditions zippertaining to the first case,in which an extra linewire is employed, the said extra wire being in dependent of the wire which conveys the telephonic current, which latter I shallhereinafter designate as the main wire. The extrawire, running parallel to the main wire, is exposed in common therewith to similar inductive action from the interfering wire or wires, and I combine the results of the inductive action in the main wire with those in the extra wire in such a manner as to counterbalance one another in the receiving-telephone.

The action of the ordinary receiving-telephone depends on the variationin the magnetization of the permanent magnet contained in the telephone, and it is most desirable that this variation should be perceptibly effected only by the varying currents developed in the transmitter. The effect of induction on the telephone-wire is to either increase or decrease the normal magnetizationin an irregular man- IOO ner,so as to interfere perceptibly with the successful reproduction of articulate speech, and to render the same indistinct. By the addition of the extra wire the proper amount of magnetization in the receiving-telephone is again restored. To enable this extra wire to act on the receiving-telephone I employ two bobbins or helices on the core of the magnet of the said receiving-telephone, both wound with wire of the same size and length; but one of the two bobbinss ay the one included in the main-line circuitis wound with a righthanded helix, while the other bobbin (that included in the circuit of the extra wire) is wound left handed. If the two wires are equidistant from a third and disturbing-wire, the current induced by the said disturbing-wire will have an equal strength in both main and extra wire, provided both are of the same length and that the resistance of both lines is the same; but the effect .of these induced currents on the magnet of the telephone will be null, as the currents pass through the helices in opposite ditm wire.

rection, and the magnet will therefore be subject and respond only to the variations of current produced in thetransmitter.

In the drawings, Figure 1 is a theoretical diagram representing the arrangement of the main and extra wire, and Fig. 2 an enlarged View of the mode in which the helices encircle the receiving-telephone magnet.

A represents the main line, C the transmitter, D the receiving-telephone, and B the ex- The telephone D is provided with two spools or bobbins oppositely wound, I) being in circuit with the main wire A, and c in circuit with the extra wire B. Both main and extra wires are connected with the ground G at both termini. A rheostat or variable resistance, E, is inserted in the circuit of the wire B near the receiving-telephone, for a purpose which will be hereinafter explained.

In Fig. 2, which represents on a larger scale the active end of the receivingtelephone magnet and core, a few convolutions of each wire are shown as encircling the core a, these indi ively, with the main and extra line wires. They are shown in diagram for greater clearness.

I shall now proceed to show the inductive action of athird wire running parallel to A and B, and conveying currents varying in strength, duration, or direction. It should be here understood that the wires A and B are supposed to be substantially equal in resistance and length and equally distant from the third wire. Under th ese conditions the induced eurrentsin A and B are of the same direction and are equal in strength. If, now, the induced currents are of. the direction indicated by the arrows in Fig. 2, they will traverse the coils b, and c in the direction also therein indicated, and their effect upon the magnet will be thus neutralized. In the event of the induced currents being of opposite direction, theultimate result would obviously be the same.

In this. way the inductive effect of a currcntin a third wire is counterbalanced or compensated in regard to the effect on the telephone. I'have so far assumed that the wires A and B are equidistant from the third and interfering wire; but it is not possible that such a condition can always occur. If the extra wire B is nearer to the disturbing-wire, the current'induced in B by the said wire will be stronger than the one simultaneously induced in A; or, if the extra wire B is more distant than A from the disturbiiigwire, the current induced in B by the said wire will be weaker than that induced in A. In order to counterbalance these con ditions, I introduce, as hereinbefore stated, the

adjustable resistance E into the circuit of the A and B are equidistant from the disturbingwire and equal in length and specific resistance, it is obvious that the adjustable resistance is not necessary. I have, however, found it very convenient in any event to insert a standard resistance, E, in the circuit of B, which may be decreased if the induced currents in B become weaker than those in A, or which may be increased if the currents in B become stronger than those in A. This arrangement is advantageous in view of the varying conditions which take place in circuits, arising from atmospheric or other causes, over which the terminal offices have no direct control, and by which circuits which are normally similar in all respects are frequently caused to differ materially. The adjustable resistance E may thus be varied and adjusted in such a way as to make the effect of induction from a third wire disappear in the telephone. To facilitate the adjustment, another variable resist-v The most convenient way to I ance, E, may, if desired, be introduced into the main-line circuit.

Having now shown that in this arrangement the induction from a third wire has no' effect the helix c of the wire B are-(oppositely wound to those in the helix b of the wire a. If the current inthe main line decreases, the induced current in the extra wire will have the same direction as .the current in the main wire, and if'the latter one tends to diminish the magnetism of the receiving-magnet, the induced current in the extra wire'will, by passing round thecore' in an opposite direction, by means of its opp ositely-wound helix, tend to still further and the extra wire and auxiliary helix in circuit therewith will therefore aid in increasing the efficiency of the telephone. I have so far assumed that the wires A and Bare of equal length; but this is not essential, for if the length of the extra wire B is but one-tenth of the main wire A, the electro-motive force of the induced current will be but onetenth of the amount formerly obtained, and if, now. the resistance of wire Bis made but one-tenth of what it was before, the current in the helix thereof, surrounding the core a of the receiving-telephone, would have the same strength as before. It is therefore evident that the tra wire B may be of any length, while its effeet can be always adjusted in such a way as to annul the effect of induction from a third,

mitter; D, the receiver, having the oppositely-wound helices b and c. The secondary helix d of the induction-coil now takes the place and assumes the functions of the extra wire B in the former cases. This secondary coil isin circuit with the coil 0 of the receiving-telephone and with the rheostat or adjustable resistance E, the said resistance being introduced for the hereinbefore-described purposes. The induction-coils may be made adjustable, and by means of such adjustment and of the variable resistance E the effects of induction on small compass.

the wire A are subdued and overcome, being neutralized by a counter-induction set up by the same disturbing-force exerted through the telephone in an opposite direction to that of the original disturbing-currents, as fully explained above. The secondary wire of the induction-coil K' has exactly the same functionas the extra wire B, and is practically'an electrical equivalent therefor, condensed into a When the action of every wire singly on the telephone is properly balanceththen the simultaneous action ofany number of them will correspondingly be well balanced.

Itis evident that instead of one neutralizing-coil, 0, there may be as many such coils as there are induction-coils K; but this would not improve the general result, and would be a needless complication.

I will observein conclusion that the essential feature of my invention is that the inductive disturbances are annulledby a compensating action which takes place in the telephone itself, by means of an additional and opposing action of another induction current, produced from the samesource as the original disturbing-current, the effect of which in the said telephone is to exactly counterbalance the disturbance caused by the induction-currents in the line wire, the final result of this compensation being the reproduction of speech in the telephone in a manner as free from interfering noises as if no induction in. the line-wire had taken pl ace.

So far as I am aware all attempts to eradicate or neutralize the hurtful effects of telephonic induction prior to my invention. were made upon the line-wire itself, with the intention of accomplishing the said neutralization in the line-circuit. In contradistinction to all such methods I eflect the desired result in the receiving-instrulnent, which may be done much more conveniently.

I may of course, if I so prefer, instead of placing two separate helices upon the magnetic core of the telephone, wind a single bobbin or spool difi'erentiallyin a manner well understood, and in that case the two wires of the differential spool would be reversely connected with the main and compensating circuits, by which the same object would be effected in a slightly different manner.

It will be understood that although I have herein described my invention with reference to butono receiving-telephone it is equally adapted for application atboth or all stations of a telephonic line, the said application being at each station simply a duplication of the arrangements and i'nstrumentalities "which I have described. I

I make no claim herein to the combination, in a telephone system wherein the telephonewire is subject to inductive interference from adjacent wires, of a differentially-wound telephone with a {telephone-wire connected in circuit with one of the helices of said telephone, and an induction-coil having its secondary coil connected in circuit with the other helix of the said telephone and its primary coil in the circuit of the disturbing-wire, or of such a combination with the addition of a rheostat or variable resistance included in the secondary circuit of the induction-coil, reserving the same for a separate application for Letters Patent; but

\Vhat I do claim is 1. The combination, substantially as hereinbefore described, of a main telephone-circuit, a compensating-circuit, and a receiving-telephone provided with differentiallywound coils or helices, one of the said helices being included in each of the said circuits.

2. A main telephone-circuit, and an induction compensating-circuit therefor, combined with a receiving-telephone having two sepa rate coils or helices surrounding the magnetic core thereof, one of the said coils being in- 4 f I 286,577 I 1 cluded in each of the said circuits, and an adustable resistance in the compensatingcircuit, substantially as set forth and for the pured to be included in a compensating-circuit,

for the specified purpose.

l 5. The combination, in a system of electric telephony, of a main telephone-line, an auxiliary or compensating line parallelto the said main line,- and a receiving-telephone having its magnetic core encircled by two operatingcoils, one for and included in each of the said line-circuits, but wound oppositely or differentially with reference to one another, where by interfering currents induced in the main line wire from, an adjacent line-wire conveying other electric currents may be counterbal anced in the receiving-teleph one by the action of similar currents induced by the said disturbing-wire in the compensating-line circuit, and caused to circulate through the said telephone by means of the second helix in an opposite direction.

6. The combination, in a system of telephonic communication, of a main telephoneline, an extra or compensating line, a receiving-telephone differentially wound, one of the differential coils being in the circuit of the main line and the other in the compensatingline, a rheostat or adjustable resistance in the compensating-line, and a second adjustable resistance in the main line, for the purpose of cooperating in regulating the action of the helices upon the magnetic core thereof, substantially as described. r

7. The combination of a main telephoneline, an auxiliary or compensating line parallel thereto, a receiving-telephone having its magnetic core surrounded by two separate coils or helices, one of the said helices being included in the main line and the other in the compensating-line, and a rheostat or adjust able resistance in the compensating line, whereby any inductive disturbance in the telephone due to induction-currents in the telepone main-line helix is counterbalanced by the circulation of similar induction-currents in an opposite direction in the compensating-helix,

and whereby the induction-currents in the auxiliary line may be caused to balance the induction-currents in the main line, irrespective of variation in, the distance of the two wires from the cause of disturbance, by varying the resistance of the said auxiliary line, as described.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 5th day of May, 1883.

ALEX- BERNSTEIN. Witnesses: GEO. WILLIS PIERCE,

Tnos. D. LocKwooD. 

